Solar chimney combined with active cooling systems for enhanced indoor comfort and energy efficiency under extreme climates: A data-driven optimization approach

Abstract

Climate change and its associated extreme events challenge the effectiveness of passive building design strategies. Hybrid passive-active systems emerge as a promising solution; however, their resilience in extreme climate conditions is less studied. This study addresses this gap by investigating the integration of solar chimneys (SC) with variable refrigerant flow (VRF) systems to improve thermal comfort and reduce energy demand under typical and extreme climate conditions. A novel combined optimization framework using Bayesian Optimization with Extreme Gradient Boosting (BO-XGBoost) and NSGA-II is applied to optimize SC design and VRF operation across future scenarios, including power outages and extreme warm periods.

Results show that the optimized SC–VRF system significantly improves resilience, particularly under extreme warm conditions. Compared to typical near-term conditions (2010–2039), Indoor Discomfort Degree and Predicted Percentage of Dissatisfied increased by 18.5 % and 1.4 % in the long-term (2070–2099) under active operation. In passive mode, these increases reached 39.7 % and 12.7 %, highlighting the limits of passive cooling alone. Sensitivity analysis indicated the SC opening area as the most influential design factor. The best overall performance was observed under typical mid-term (2040–2069) conditions, with energy use reduced by 13.3 % compared to long-term and 9.5 % compared to near-term scenarios. While passive SCs show potential in the near-term, integrating them with VRF systems is essential for maintaining comfort and efficiency under future extremes. The proposed SC–VRF configuration offers an effective strategy for maintaining thermal comfort and reducing energy use under climate extremes, thereby enhancing the climate resilience of buildings.